The proposed research is designed to further our understanding of physiological changes which occur in the reproductive systems of aged monkeys. Preliminary evidence from our laboratory indicates that during senescence the reproductive system of the rhesus monkey undergoes very similar changes to those changes reported in humans. Initial studies have been designed to compare the patterns of pituitary gonadotropin and prolactin secretion as well as the gonadal steroid output in senescent and young adult animals. Utilizing these data, studies will be designed to explore possible changes in the sensitivities of the testes, ovaries, uterus, anterior pituitary and hypothalamus of aged animals to specific hormonal stimulation and/or inhibition. In addition, other endocrine tissues will be examined for possible age-related changes in their function and if found studies will be undertaken to examine the possible interrelationships between the specific endocrine system and the reproductive system. These results should help determine if the physiological function of the specific tissue being studied is (1) the consequence of aging within that tissue per se, (2) due to aging changes in other regulatory tissue(s), or (3) a general aging effect on all tissues being examined.